1. Field of the Invention
The present invention relates to a simple construction for cooling operating oil filling a housing for an axle driving apparatus for transmitting a variable speed drive force from a hydrostatic transmission to axles.
2. Related Art
It is well known to dispose a cooling hose in the vicinity of a fan driven by power from an engine and send operating oil from a hydrostatic transmission to the cooling hose to thereby cool the operating oil. This is disclosed in, for example, U.S. Pat. Nos. 3,727,712; 3,362,161 and in Japanese Utility Model Laid-Open Gazette No. Sho 60-89453.
The above-mentioned examples are constructed so that only the operating oil used for the hydrostatic transmission is cooled, while the temperature of the lubricating oil for lubricating gears or shafts housed in the housing rises, leading to a temperature rise of the housing itself. When this lubricating oil serves as operating oil, and the oil is used in an external hydraulic actuator, the temperature of the operating oil may increase so much as to cause a malfunction.